Phase change memory device and method for fabricating the same
A phase change memory device is provided. The phase change memory device includes a substrate with a first electrode layer formed thereon. A first phase change memory structure is on the first electrode layer and electrically connected to the first electrode layer. A second phase change memory structure is on the first phase change memory structure and electrically connected to the first phase change memory structure, wherein the first or second phase change memory structure includes a cup-shaped heating electrode. A first insulating layer covers a portion of the cup-shaped heating electrode along a first direction. A first electrode structure covers a portion of the first insulating layer and the cup-shaped heating electrode along a second direction. The first electrode structure includes a pair of phase change material sidewalls on a pair of sidewalls of the first electrode structure and covering a portion of the cup-shaped heating electrode.
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1. Field of the Invention
The invention relates to a phase change memory device and method for fabricating the same, and more particularly to a phase change memory device with relatively higher device density and a method for fabricating the same.
2. Description of the Related Art
A phase change memory (PCM) device may potentially serve as a 64-megabyte (MB) or greater stand-alone non-volatile memory. Before PCM devices become a mainstream replacement for flash memory, however, they must first achieve excellent electrical and thermal performance. Fabrication of non-volatile memory with relatively higher device density using the conventional fabricating process is, thus, a major aim of researchers.
U.S. Pat. No. 6,501,111 issued by Intel Corporation discloses a conventional three-dimensional PCM (3D-PCM) 212 with a cup-shaped bottom electrode 206 as shown in
A PCM device with a higher device density and not limited by photolithography resolution is desirable.
BRIEF SUMMARY OF INVENTIONA detailed description is given in the following embodiments with reference to the accompanying drawings.
The invention provides a phase change memory device and method for fabricating the same. An exemplary embodiment of a phase change memory device comprises a substrate. A first electrode layer is formed on the substrate. A first phase change memory structure is formed on the first electrode layer and electrically connected to the first electrode layer. A second phase change memory structure is formed on the first phase change memory structure and electrically connected to the first phase change memory structure. The first phase change memory structure or the second phase change memory structure comprises a cup-shaped heating electrode disposed in a first dielectric layer. A first insulating layer is disposed on the first dielectric layer along a first direction covering a portion of the cup-shaped heating electrode. A second dielectric layer is disposed on the first insulating layer and the first dielectric layer. A first electrode structure is disposed in the second dielectric layer along a second direction and covering a portion of the first insulating layer and the cup-shaped heating electrode. The first electrode structure comprises a pair of phase change material spacers disposed on a pair of sidewalls of the first electrode structure covering a portion of the cup-shaped heating electrode.
A method of fabricating a phase change memory device comprises providing a substrate with a first electrode structure formed thereon. A first phase change memory structure is formed on the first electrode and electrically connected to the first electrode. A second phase change memory structure is formed on the first phase change memory structure and electrically connected to the first phase change memory structure. The first phase change memory structure or the second phase change memory structure comprises forming a cup-shaped heating electrode in a first dielectric layer. A first insulating layer is formed on the first dielectric layer along a first direction covering a portion of the cup-shaped heating electrode. A first electrode structure is formed along a second direction covering a portion of the first insulating layer and the cup-shaped heating electrode. The first electrode structure comprises a pair of phase change material spacers disposed on a pair of sidewalls of the electrode structure and covering a portion of the cup-shaped heating electrode. A second dielectric layer is formed on the first insulating layer and the first dielectric layer and adjacent the first electrode structure.
The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
Next, a p-type semiconductor layer and an n-type semiconductor layer (not shown) are formed on the first electrode layer 302 by thin film deposition such as CVD. A portion of the p-type semiconductor layer and an n-type semiconductor are then removed to form a diode 308 by photolithography and etching processes. The diode 308 may be a semiconductor composite layer, preferably a stack of an n-type impurity doped semiconductor layer and a p-type impurity doped semiconductor layer to form a p-n junction. The n-type impurity may comprise phosphorous (P) or arsenic (As), and the p-type impurity may comprise boron (B) or difluoroborane (BF2). Alternatively, the diode 308 may comprise polycrystalline semiconductor materials or amorphous semiconductor materials such as polysilicon or amorphous silicon.
Next, a first dielectric layer 304 is formed on the first electrode layer 302 and the diode 308 as the diode 308 is covered by thin film deposition such as CVD. The first dielectric layer 304 may comprise silicon dioxide (SiO2), silicon nitride (SiNX) or the like. The first dielectric layer 304 is then covered with a patterned photoresist to define the position of a cup-shaped opening 306, and subsequent anisotropic etching to remove the first dielectric layer not covered by the patterned photoresist until the diode 308 is exposed. Next, the patterned photoresist is removed to form a cup-shaped opening 306. The bottom of the cup-shaped opening 306 is directly on top of the diode 308. An aperture of the cup-shaped opening 306 is related to a thickness of subsequently formed phase change material spacers. In one embodiment, the aperture of the cup-shaped opening 306 is preferably about 0.2 cm.
Referring to
As shown in
The first exemplary embodiment of the phase change memory device 100a mainly comprises: a substrate 300; a first electrode layer 302 formed on the substrate 300; a first phase change memory structure 400a formed on the first electrode layer 302 and electrically connected to the first electrode layer 302; a second phase change memory structure 400b formed on the first phase change memory structure 400a and electrically connected to the first phase change memory structure 400a, wherein the first phase change memory structure 400a or the second phase change memory structure 400b comprises a cup-shaped heating electrode 314 disposed in a first dielectric layer 304; a first insulating layer 318 disposed on the first dielectric layer 304 along a first direction 316 and covering a portion of the cup-shaped heating electrode 314; a second dielectric layer 332 disposed on the first insulating layer 318 and the first dielectric layer 304; a first electrode structure 331 disposed in the second dielectric layer 332 along a second direction 319 and covering a portion of the first insulating layer 318 and the cup-shaped heating electrode 314, wherein the first electrode structure 331 comprises a pair of phase change material spacers 330a disposed on a pair of sidewalls 328 of the first electrode structure 331 and covering a portion of the cup-shaped heating electrode 314.
Some advantages of an exemplary embodiment of the 3D phase change memory device 100a and 100b are described in the following. The phase change memory device is a unit memory cell with multi-bits, referred to as a multi-level cell (MLC). The top electrode of the lower phase change memory structure is shared with the bottom electrode of the upper phase change memory structure, thus, process cycle time can be reduced. Lastly, by controlling the contact area between the phase change material spacer and the conductive layer via an intersecting area of the phase change material spacer and the conductive layer controls the contact area is minimized.
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
Claims
1. A phase change memory device, comprising:
- a substrate;
- a first electrode layer formed on the substrate;
- a first phase change memory structure formed on the first electrode layer and electrically connected to the first electrode layer;
- a second phase change memory structure formed on the first phase change memory structure and electrically connected to the first phase change memory structure, wherein the first phase change memory structure or the second phase change memory structure comprises: a cup-shaped heating electrode disposed in a first dielectric layer; a first insulating layer disposed on the first dielectric layer along a first direction and covering a portion of the cup-shaped heating electrode; a second dielectric layer disposed on the first insulating layer and the first dielectric layer; and a first electrode structure disposed in the second dielectric layer along a second direction and covers a portion of the first insulating layer and the cup-shaped heating electrode, wherein the first electrode structure comprises a pair of phase change material spacers disposed on a pair of sidewalls of the first electrode structure and covering a portion of the cup-shaped heating electrode.
2. The phase change memory device as claimed in claim 1, further comprising:
- a second insulating layer and a second electrode layer formed between the first phase memory structure and the second phase change memory structure sequentially, wherein the second electrode layer is electrically connected to the second phase change memory structure.
3. The phase change memory device as claimed in claim 1, the cup-shaped heating electrode further comprising:
- a diode structure;
- a conductive layer disposed on the diode, wherein the conductive layer is cup-shaped and comprise an opening; and
- an insulating layer filled in the opening.
4. The phase change memory device as claimed in claim 3, wherein the conductive layer has a thickness of about 1 nm to 300 nm.
5. The phase change memory device as claimed in claim 3, wherein the conductive layer comprises metals, alloys, metal compounds, semiconductor materials or combinations thereof.
6. The phase change memory device as claimed in claim 5, wherein the metal comprises aluminum (Al), copper (Cu), cobalt (Co), tantalum (Ta), nickel (Ni), titanium (Ti), tungsten (W) or combinations thereof.
7. The phase change memory device as claimed in claim 5, wherein the alloy comprises aluminum-alloy, copper-alloy, cobalt-alloy, tantalum-alloy, nickel-alloy, titanium-alloy, tungsten-alloy, TiW, GaSb, GeTe, Ge2Sb2Te5, Ag—In—Sb—Te or combinations thereof.
8. The phase change memory device as claimed in claim 5, wherein the metal compound comprises CoN, TaN, NiN, TiN, WN, CoSiXNY, TaSiXNY, NiSiXNY, TiSiXNY, WSiXNY, Co-salicide (CoSiX), Ta-salicide (TaSiX), Ni-salicide (NiSiX), Ti-salicide (TiSiX), W-salicide (WSiX), yttrium barium copper oxide (YBCO), Cu2O, indium tin oxide (ITO) or combinations thereof.
9. The phase change memory device as claimed in claim 5, wherein the semiconductor material comprises polycrystalline semiconductor material, amorphous semiconductor material or combinations thereof.
10. The phase change memory device as claimed in claim 1, wherein the first insulating layer covers half the cup-shaped heating electrode.
11. The phase change memory device as claimed in claim 1, wherein the first electrode structure covers one quarter of the cup-shaped heating electrode.
12. The phase change memory device as claimed in claim 1, wherein the first electrode structure is a composite layer comprising a fourth insulating layer and a conductive layer.
13. The phase change memory device as claimed in claim 12, wherein the conductive layer comprises metals, alloys, metal compounds, semiconductor materials or combinations thereof.
14. The phase change memory device as claimed in claim 13, wherein the metal comprises aluminum (Al), copper (Cu), cobalt (Co), tantalum (Ta), nickel (Ni), titanium (Ti), tungsten (W) or combinations thereof.
15. The phase change memory device as claimed in claim 13, wherein the alloy comprises aluminum-alloy, copper-alloy, cobalt-alloy, tantalum-alloy, nickel-alloy, titanium-alloy, tungsten-alloy, TiW, GaSb, GeTe, Ge2Sb2Te5, Ag—In—Sb—Te alloy or combinations thereof.
16. The phase change memory device as claimed in claim 13, wherein the metal compound comprises CoN, TaN, NiN, TiN, WN, CoSiXNY, TaSiXNY, NiSiXNY, TiSiXNY, WSiXNY, Co-salicide (CoSiX), Ta-salicide (TaSiX), Ni-salicide (NiSiX), Ti-salicide (TiSiX), W-salicide (WSiX), yttrium barium copper oxide (YBCO), Cu2O, indium tin oxide (ITO) or combinations thereof.
17. The phase change memory device as claimed in claim 13, wherein the semiconductor material comprises polycrystalline semiconductor material, amorphous semiconductor material or combinations thereof.
18. The phase change memory device as claimed in claim 13, wherein the conductive layer comprises single layer or stacked layers.
19. The phase change memory device as claimed in claim 1, wherein the first direction is perpendicular to the second direction.
20. The phase change memory device as claimed in claim 1, wherein the phase change material spacers of the first phase change memory structure is perpendicular or parallel to the phase change material spacers of the second phase change memory structure.
21. The phase change memory device as claimed in claim 1, wherein the first insulating layer and the first dielectric layer have an etching selectivity of about 1 to 1000.
22. The phase change memory device as claimed in claim 1, wherein a height of the phase change material spacer is less than a height of the first electrode structure.
23. A method of fabricating a phase change memory device, comprising:
- providing a substrate with a first electrode layer formed thereon;
- forming a first phase change memory structure on the first electrode layer and electrically connected to the first electrode layer;
- forming a second phase change memory structure on the first phase change memory structure and electrically connected to the first phase change memory structure, wherein the first phase change memory structure or the second phase change memory structure comprises: forming a cup-shaped heating electrode in a first dielectric layer; forming a first insulating layer on the first dielectric layer along a first direction covering a portion of the cup-shaped heating electrode; forming a first electrode structure along a second direction and covering a portion of the first insulating layer and the cup-shaped heating electrode, wherein the first electrode structure comprises a pair of phase change material spacers disposed on a pair of sidewalls of the electrode structure covering a portion of the cup-shaped heating electrode; and forming a second dielectric layer on the first insulating layer and the first dielectric layer and adjacent the first electrode structure.
24. The method of fabricating the phase change memory device as claimed in claim 23, further comprising:
- sequentially forming a second insulating layer and a second electrode layer between the first phase memory structure and the second phase change memory structure, wherein the second electrode layer is electrically connected to the second phase change memory structure.
25. The method of fabricating the phase change memory device as claimed in claim 23, further comprising:
- forming a p-type semiconductor layer and an n-type semiconductor layer on the first electrode layer by thin film deposition;
- removing a portion of the p-type semiconductor layer and the n-type semiconductor to form a diode by photolithography and etching processes;
- forming a first dielectric layer on the first electrode layer and the diode with covering the diode before forming the cup-shaped heating electrode.
26. The method of fabricating the phase change memory device as claimed in claim 25, further comprising:
- removing a portion of the first dielectric layer until the diode is exposed forming a cup-shaped opening by photolithography and etching processes;
- forming a conductive layer in the cup-shaped opening, wherein the conductive layer is cup-shaped;
- forming a third insulating layer on the conductive layer, the third insulating layer filling the cup-shaped opening; and
- performing a planarized process to remove a portion of the conductive layer and the third insulation layer to form the cup-shaped heating electrode.
27. The method of fabricating the phase change memory device as claimed in claim 23, wherein the first insulating layer covers one half of the cup-shaped heating electrode.
28. The method of fabricating the phase change memory device as claimed in claim 23, wherein the first electrode structure covers one quarter of the cup-shaped heating electrode.
29. The method of fabricating the phase change memory device as claimed in claim 23, further comprising:
- forming a stacked structure comprising a fourth insulating layer and a conductive layer on the first dielectric layer;
- covering a phase change material layer on the stacked structure; and
- removing a portion of the phase change material layer by anisotropic etching to form a pair of phase change material spacers on a pair of sidewall of the stacked structure to form the first electrode structure.
Type: Application
Filed: May 7, 2007
Publication Date: Jul 10, 2008
Patent Grant number: 7732801
Applicant:
Inventor: Wei-Su Chen (Hsinchu)
Application Number: 11/797,730
International Classification: H01L 45/00 (20060101);